> It's probably been endemic in humans It probably was endemic, as it was declared eradicated in 1979 by an effective vaccination campaign. More importantly,

> It's probably been endemic in humans It probably was endemic, as it was declared eradicated in 1979 by an effective vaccination campaign. More importantly, though, smallpox, as a complex DNA virus, had far fewer viable mutations. That fact, along with an apparent lack of non-human reservoirs, is probably why it could be eradicated.